The invention relates to a stereomicroscope.
Stereomicroscopes having a capability for adjusting the stereo base are described in U.S. Pat. No. 3,818,125 (Butterfield, 1971). Although different variations of possibilities for varying the stereo base are described there, such devices have not become widespread in practice. This is in spite of the fact that the disadvantages which are known and specified by Butterfield in the case of stereomicroscopes without stereo base adjustment are still present. To this extent, reference is made to the relevant description partsxe2x80x94in particular in column 2, lines 43-62xe2x80x94in Butterfield, which count as disclosed herein. The reason for not using the teachings of Butterfield apparently lies in various problems which result from his solution proposals. Thus, for example, the use of prisms is excluded (e.g. FIGS. 5-9 in Butterfield), since, as Butterfield himself admits (column 9, lines 65 and 66 of Butterfield), these are accompanied by color aberrations which can have a negative influence on the color quality of the viewed image. The variations proposed by Butterfield having displaceable aperture diaphragms (10, e.g. FIGS. 2 and 5) furthermore have the disadvantage that as a result of a displacement of the latter not only is the stereo base adjusted but in addition the image brightness is darkened or changed, which can disadvantageously lead to too low a light yield, in particular in the case of small stereo bases.
Similar disadvantages occur in the case of the solution proposal in accordance with FIG. 10 of Butterfield. To be specific, as a result of the pivoting of the mirror (50), not only is the stereo base adjusted, but the aperture is also changed, which in turn can lead to corresponding light losses.
The variants proposed by Butterfield according to FIGS. 11 and 12 are in turn complicated and can be implemented only with difficulty to the extent that two parallel lens systems (54) are necessary there, which are associated with a corresponding increase in price and also a corresponding increase in constructional size, with further penalties in terms of light as a result of possibly too small an aperture. Furthermore, it is generally also difficult to adjust such parallel lens systems such that they have identical properties. However, if the properties are not identical, this can lead to fatigue in the observer, in particular if a video camera and monitor are connected in front of said observer, since he does not have the possibility of recorrecting individually, as in the case of two eyepiece beam paths.
It is therefore an object of the present invention to develop a system which, in spite of a variable stereo base, does not reduce the light intensity in the beam pathxe2x80x94at least for a certain period and for each beam path separatelyxe2x80x94by a significant amount. In addition, it is intended to enable recordingsxe2x80x94as known per sexe2x80x94using only a single image recording device, for example using a single video camera. Preferably, it is furthermore intended to provide only one main objective and to restrict the constructional size of the stereomicroscope to a minimum.
This object is achieved, for example, by means of the features described herein. As a result of the arrangement of the adjusting device behind the main objective, there is an integrated construction with low light losses and without the disadvantages listed above.
A practical application of the invention results, for example, in the case of video stereomicroscopes.
For such microscopes, but also for other microscopes, a special development of the invention is proposed which can also be applied independently of the invention. To explain the background:
Microscopes often have beam splitters in order to duplicate the beam path directed towards the object to be magnified.
Often provided on split beam paths are, inter alia, additional observer eyepieces, phototubes, camera connections or displays of all types, the images from which are intended to be insertedxe2x80x94that is to say superimposed on the image of the viewed object. This applies in particular also to stereomicroscopes which have an image recording device for producing a stereo view on a 3D displayxe2x80x94possibly remote from the microscope.
For the last application, from time to time such an image recording device (e.g. a CCD each) is provided both for the beam path assigned to the left eye and also for the beam path assigned to the right eye.
For the application having the inserted display, in an analogous manner a display (e.g. a CRT each) is provided for the beam path assigned to the left and also to the right eye.
These known stereomicroscopes thus have the disadvantage that two magnification devices (zoom, turret) and two image recording devices or two displays, together with appropriate optics, are necessary. In this case, the left and right image recording devices or optics must be mutually adjusted.
In other known stereomicroscopes there are also solutions having only a single image recording device. There, both the left and the right beam path or the ray bundle located in them are alternately fed to the single image recording device. As a result of such a construction, a second image recording device is saved and, inter alia, the serial recording of a stereoimage pair on one video recording device is facilitated. The changeover process between the two beam paths is in this case achieved using beam splitters and shutters which block off the respective undesired bundle of rays via polarization changes using correspondingly arranged analyzers.
Such a stereomicroscope having geometric superimposition of the right and left frames is described, for example, in U.S. Pat. No. 5,007,715.
The system which is described in U.S. Pat. No. 5,007,715 has the disadvantage that, both during the polarization (about 50%) and during the superimposition (about 50%) of the two polarized bundles of rays by means of a beam splitter, up to 80% of the light intensity which is present of the respective bundles of rays (100%) are lost. A partial superimposition of the two different sets of image information from the right and left image beam paths can make itself noticeable as a further disadvantage if the darkening by the analyzers is not 100%, which can primarily also occur if the polarizers do not operate satisfactorily. Since however it is precisely in microscopes that the brightness on the object to be viewed cannot be arbitrarily increased, the permanent loss in light intensity is disadvantageous. The partial superimposition, on the other hand, can lead to unnecessary stresses for the organs of sight of the observer.
A similar known system is described in U.S. Pat. No. 5,003,385, where likewise about 80% of the light intensity of the left and right beam paths are absorbed before the light is incident on the single camera.
A somewhat different system, where the polarization of the light remains unconsidered, is described in U.S. Pat. No. 5,028,994. There, the light from two first beam paths (left and right beam path) is firstly fed in each case to an LC shutter (twisted nematic type), which can open or close the relevant beam path. The two beam paths are incidentxe2x80x94deflected via mirrorsxe2x80x94on a beam splitter. If one shutter is open, then the second shutter is closed, for which reason theoretically it is always only possible for light from one of the two first beam paths to arrive at the camera arranged downstream of the beam splitter. At the beam splitter, in each case about 50% of the light intensity is lost; likewise at the shutter, even in the xe2x80x9copen conditionxe2x80x9d, about 50% in each case is lost, since the described shutter structure (cf. column 2 line 48 to column 3 line 29) permit only light of a specific polarization direction to pass through. In addition, in the case of the described shutter, the abovementioned disadvantages of partial superimposition may also occur.
It is therefore an object of the present development to develop a system which reduces the light intensity in the beam pathxe2x80x94at least for a specific period and separately for each beam pathxe2x80x94in the case of using beam splitters at a maximum to the extent of the light intensity lost there (as a rule about 50%). In other words: a gain of about 50% of the light intensityxe2x80x94both in the case of recording and in the case of the insertion of imagesxe2x80x94is intended to be possible by contrast with conventional stereomicroscopes, although only a single image recording device or only a single display is provided for both beam paths. Furthermore, the superimposition between the right and the left image beam path is intended to be excluded.
This additional object is achieved by means of features described below. The same problems or the same objects for microscopes having images to be reflected in instead of images to be recorded are also solved for the first time.
For the specific further processing of video images which have been obtained using a video stereomicroscope according to the invention, reference is made to the PCT patent application, having priorities of the three applications CH3890/93-3; CH135/94-3 and CH198/94-5 (now U.S. Pat. Nos. 5,870,137 and 6,040,852), which also count as lying within the scope of this disclosure. All the applications mentioned together, and the inventions on which they are based, are symbiotically complementary in the case of corresponding exemplary embodiments.
The geometrical superimposition of a left and right stereobeam path then enables the recording of the two beam paths by only one video camera, with the result that images located alongside one another can be recorded successively in time and further processed. This develop- ment of the invention thus also enables the reproduction of images via one monitor, as described for example in U.S. Pat. No. 5,007,715. The statements disclosed in relation to the figure in the abstract also count as disclosed herein.
The use according to the invention of mechanical aperture diaphragms which either completely reflect light or allow light to pass through completely, has the effect, at least during the respective duration of a specific switching position of the aperture diaphragm, of forwarding the complete light intensity of the light located in the relevant beam path. The encoding process for the light, such as for example in the use of polarization, as also proposed by Butterfield, is therefore dispensed with. In this case, only insertion or blanking out is used. This results in a gain in intensity of up to over 200%, compared with known arrangements having splitters and polarization filters. An undesired superimposition of two beam paths is excludedxe2x80x94advantageously by contrast with the use of polarization. As a result of this development of the invention, in addition the further object is thus achieved of effecting a light intensity loss which is only low, in spite of geometric beam splitting.
Although the use of mechanical aperture diaphragms in optical systemsxe2x80x94even if for completely different purposesxe2x80x94is known in principle, thus, for example, reference is made to a Nipkow disk, such as is represented for example in U.S. Pat. No. 5,067,805, or to rigid mechanical beam splitters in which, for example part of the light in the beam path is allowed through at an annular aperture diaphragm and another part is reflected back for beam splitting, these known mechanical beam splitters do not reduce the actual light intensity loss, since following the splitting, in each subsequent beam path in each case only part of the original 100% light intensity is forwarded. The other part is in fact deflected further by the splitter into the second beam path.
Individual applications having monochromatic light could reduce splitting losses at splitters to a residual, which however is not possible if it is desired to use the entire light spectrum.
A partial aspect of the invention is therefore found in the case of a microscope, in particular a stereomicroscope, having a first beam path and a beam splitter in this beam path, the beam splitter being designed as a mechanooptical or electrooptical switching element which can be transferred alternately from a reflective into a transmissive or another reflective state, one of the two states exposing the light path for the first beam path and the other state exposing the light path for a second beam path, while blocking the light path for the viewing beam path. Such a switching element thus replaces conventional beam splitters, by which means the light loss can be reduced significantly.
Within the scope of the invention there are various further types of design and variants thereto, which are described below.
In the case of a preferred variant, the entry bundles of rays of the stereomicroscope are geometrically superimposedxe2x80x94but chronologically one after the otherxe2x80x94after the (single) main objective, either by means of a rotating mirror having at least in each case one transmissive and reflective subregion or by means of a stationary splitter and a rotating aperture diaphragm which alternately covers the entry beam paths. In this case it is favorable if both beam paths have the same optical path lengths as far as the image recording device. In the sense of the invention, it is in this case not important in which form the reflecting aperture diaphragms are introduced. Translatory movements are in this case to be equated with rotating movements or other switching movements. Thus, for example, it is thus entirely possible to provide aperture diaphragms similar to photographic camera shutters, but which are appropriately silvered on at least one side. A variant having micro-mechanical lamellar mirrors is likewise conceivable, such lamellar mirrorsxe2x80x94at present these are essentially only in laboratory experimentsxe2x80x94being generally constructed from silicon and being switched by means of electrostatic charges.
If, as in one exemplary embodiment, a rotating glass disk is used which is silvered on one half, a practical, easily balanced arrangement is given thereby, which however has one small disadvantage; on the non-silvered glass half, because of the plane plate effect, an image offset occurs. In order to avoid this, in the case of a preferred variant, the glass is omitted at this point, so that a completely free light passage is possible there.
In the case of all pushed-in or turned-in aperture diaphragms, since the effect of the moving aperture diaphragm can be disadvantageous in certain circumstances for recordings on image recording devices, for example CCDS, provision is further made in some embodiments for the displacement or rotational movement to be carried out particularly rapidly and for the aperture diaphragm to remain in the switching position then assumed for a certain time. In the case of rotating aperture diaphragms, a drive having a stepping motor is particularly suitable for this. A corresponding addition or alternative for this technique results from a clocked exposure control of a video camera which is possibly being used, or a display which is being used.
If appropriate, additional light may be fed to the object via the said silvered surface via a further mirror arrangement. It might even be possible, under certain circumstances, for other more complicated illumination devices to be omitted as a result.
A further variant having a 50/50 pupil splitter is advantageous in as much as only one glass splitter per beam path is necessary and, in the eyepiece beam path, depending on the splitter effect of this glass splitter, a ratio of, for example, 25% display and 50% object or (at the eyepiece) for example 50% display and 50% object can be achieved. The first, for example, in the case of a glass splitter of about 1/1 partial effect, the latter for example using a glass splitter of about 2/2 partial effect.
A further variant, which integrates the illumination completely into the structure, results if the switching element is used twice, in that the reflecting surface is used on both sides. In the pivoted-in state, it lies at the point of intersection of the axes of the first beam paths, preferably at an angle of 45xc2x0 each to the said axes. Arranged in direct prolongation of one of the first beam paths is a light source whose light, in the pivoted-in state of the switching element, is reflected into the one beam path, whereas it falls directly into the other first beam path in the pivoted-out state. In this way, optimal illumination of a viewed object is possible.
It is further preferred to place the aperture diaphragm or the splitter mirror as close as possible to the main objective, in order to avoid vignetting of the reproduced images.
A variant having a plurality of circular segment-like reflectors reduces the required number of revolutions of a rotating mirror.
The use of plane plates as a stereo base setting is constructionally simple. The disadvantages of the use of prisms, as in Butterfield, are omitted thereby. The mechanical construction is simple to realize, miniaturization and any automatic and/or remote control is simple. Coupling to the magnification setting of the stereomicroscope and/or to a zoom setting is therefore conceivably simple. The light losses are minimum in contrast with the use of aperture diaphragms as in Butterfield.
A special design of the invention serves to reflect in information for an observer of an eyepiece beam path. All the previously mentioned specific and advantageous designs and variants can be used practically also in conjunction with this structure.
If, in conjunction with such a stereomicroscope, in each case a right and left frame of a stereoimage pair is displayed on the display, the observer thus obtains a 3D image to view, which is superimposed on the 3D image of the eyepiece beam path. Advantageously, it is possible thereby for, for example, positron ray images or magnetic resonance stereoimages to be superimposed on the currently seen images. In the case of the use of such stereomicroscope as a surgical microscope, this results in particular advantages for the surgeon, especially since he can interpret the image seen in a better way. On the other hand, the reflected-in images could also contain other information, for example about the control of devices or of the microscope itself. In this connection, reference is made to the following Swiss patent applications, whose content likewise counts as disclosed within the scope of the invention: CH3890/93-3; CH135/94-3 and CH198/94-5 (now U.S. Pat. Nos. 5,870,137 and 6,040,852). A combination of the teachings of these applications with the present application is particularly practical. In particular, a combination having mechanical beam splitters is preferred, since in this case a further light intensity gain of about 100% (a total of about 200%) is possible.
It is of course possible for the variant with the image recording device to be used simultaneously with the variant having the display, providing that a split-off beam path each is made available to both.
Instead of the mechanically moved aperture diaphragms, other types of aperture diaphragms could also be used, provided that they are only capable of changing one hundred percent between a transmitting and blocking state.
The invention is described in particular in conjunction with a stereomicroscope. In the widest sense, however, it can also be practically used with any other beam paths.